brew edit works if the file in question won't parse

bin/brew

@@ -125,7 +125,16 @@ begin
                           "#{HOMEBREW_REPOSITORY}/bin/brew"<<
                           "#{HOMEBREW_REPOSITORY}/README.md"
     else
-        exec_editor *ARGV.formulae.collect {|f| f.path}
+      # we don't use ARGV.formulae as that will throw if the file doesn't parse
+      paths = ARGV.named.collect do |name|
+        unless File.exist? path = "#{HOMEBREW_REPOSITORY}/Library/Formula/#{name}.rb"
+          require 'formula'
+          raise FormulaUnavailableError, name
+        else
+          path
+        end
+      end
+      exec_editor *paths
     end
 
     when 'up', 'update'